Central A/C Cooling

I have a Carrier HVAC system. The compressor condensor works on heat and cool. The air handler fan works sometimes. I tapped on the fan motor relay board- manager board and the fan starts sometimes.

I ordered a new fan manager board and installed it. The uiti ran perfectly for about thirty minutes and then shut off. The compressor condenser unit continued to work outside but the air handler fan went off. Where do you think the problem is? I'm an aerospace engineer and can trace most problems if some directions are given. Thanks.

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Central A/C Cooling

is there a door switch when going into the fan motor section? and jumping R to G right at the board should give you SUPPLY FAN ONLY...put stat if off on system fan in auto.do the jump at the furnace board if it works go up stairs and remove the stat and jump again R to G to see if the fan works on the jump....from the furnace board C and Y go out to the condenser for you to know when cooling calls.but check that door switch

Central A/C Cooling

Central A/C Cooling

There's no door switch. I jumped the relay switch with a jumper wire and the blower ran. I still replaced the fan motor relay board. It ran for about an hour and came to temperature set. The outside condenser still was running but the fan blower never came back on so as to blow more cool air as the temperature rose in the house.